Toner

ABSTRACT

A toner containing toner particles, each of which contains a binder resin and a colorant, and silica particles, wherein the silica particles have a volume average particle diameter (Dv) of 70 nm or more and 500 nm or less, the variation coefficient of diameters of the silica particles, based on volume distribution thereof, is 23% or less, and wherein when the silica particles are heated from 105° C. to 200° C., the ratio of mass decrease is 0.60% or less.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a toner for developing an electrostaticimage used for image forming of an electrophotographic system typifiedby a copying machine and a printer.

2. Description of the Related Art

Addition of an external additive having a large particle diameter hasbeen proposed as a technique to improve the transferability of a toner(refer to Japanese Patent Laid-Open No. 2007-171666). This proposal isdirected to improve the transferability by adding silica particleshaving large particle diameters to toner particles and reducing physicaladhesion between the toner and a photo conductor. However, the silicaparticles, which are used in this proposal and which have large particlediameters, are particles obtained by a deflagration method and,therefore, have a wide particle size distribution. Consequently, in thecase where the toner is used over a long term, particles having largeparticle diameters are eliminated from the toner easily, and particleshaving small particle diameters are embedded in toner particles easily.Furthermore, when silica particles move to concave portions of tonerparticle surfaces, it is difficult to give stable chargeability,fluidity, and transferability to the toner.

As for a technique to improve this harmful effect, addition of silicaparticles having large particle diameters with a narrow particle sizedistribution to toner particles has been proposed (refer to JapanesePatent Laid-Open No. 2007-322919). Japanese Patent Laid-Open No.2007-322919 discloses that silica particles which have large particlediameters with a sharp particle size distribution and which are producedby a sol-gel method are used, so as to improve long-term stablechargeability and improve transferability. However, silica particles,which have large particle diameters and which are obtained by thesol-gel method, in the related art are hydrophilic particles havingsilanol groups to a large extent. Therefore, even when a hydrophobizingtreatment is performed, there are large amounts of remaining silanolgroups. Consequently, the property of the silica particles to give thechargeability to the toner is influenced by the temperature and thehumidity easily, and it is difficult to give stable chargeability to thetoner. Meanwhile, in the case where large amounts of hydrophobizingagent is used for silica particles in order to improve this harmfuleffect, a property to give fluidity to the toner is degraded.Consequently, in the case where a toner including such silica particlesis used and images are output over a long term, it is difficult tomaintain high image quality.

As for a technique to improve these harmful effects, use of silicaparticles, which have silanol groups to a relatively small extent andwhich have large particle diameters with a specific particle sizedistribution, to a toner has been proposed (refer to Japanese PatentLaid-Open No. 2008-262171). However, silica particles, which have largeparticle diameters and which are used in Japanese Patent Laid-Open No.2008-262171, have a wide particle size distribution and there areproblems in properties to give the fluidity and the chargeability to atoner.

As described above, it is difficult to obtain silica particles whichhave large particle diameters and which can give stable chargeabilityand fluidity to a toner regardless of environment.

SUMMARY OF THE INVENTION

The present invention provides a toner having stable chargeability andfluidity regardless of environment. Furthermore, the present inventionprovides a toner which can produce a high-definition high-quality imageover a long term stably in the case where the toner is used for imageforming.

The present invention relates to a toner containing toner particles,each of which contains a binder resin and a colorant, and silicaparticles, wherein the above described silica particles have a volumeaverage particle diameter (Dv) of 70 nm or more and 500 nm or less, thevariation coefficient of diameters of the silica particles, based onvolume distribution thereof, is 23% or less, and wherein when heatingthe silica particles to measure the mass variation, the ratio of massdecrease of the silica particles at the temperature in the range of 105°C. to 200° C. is 0.60% or less.

The toner according to the present invention has stable chargeabilityand fluidity regardless of environment. Furthermore, in the case wherethe toner according to the present invention is used for image forming,a high-definition high-quality image can be produced over a long termstably.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments.

DESCRIPTION OF THE EMBODIMENTS

The present inventors performed intensive research on the properties ofsilica particles having large particle diameters with respect to atoner, to which silica particles having large particle diameters areadded externally. As a result, it was found that the above describedproblems were able to be solved by adding the silica particles, whichhave large particle diameters and having the following properties, tothe toner externally.

The silica particles used in the present invention are silica particleshaving large particle diameters and having a volume average particlediameter (Dv) of 70 nm or more and 500 nm or less. In the case where thevolume average particle diameter is more than 500 nm, the fluidity ofthe toner is hindered and, in addition, silica particles are eliminatedfrom the toner surface easily. Therefore, such silica particles cannotgive long-term stable chargeability and fluidity to the toner.Furthermore, eliminated silica particles adhere to developing agentconstituent materials and image forming system members or contaminatethem. Consequently, degradation in charge characteristics and anoccurrence of toner scattering may be caused. On the other hand, in thecase where the volume average particle diameter of the silica particlesis less than 70 nm, a sufficient spacer effect of silica particleshaving large particle diameters is not exerted. Therefore, in the casewhere such silica particles are used for the toner, degradation of thetoner transferability and degradation of the toner surface may occur.The volume average particle diameter (Dv) of the silica particles ispreferably 80 nm or more and 200 nm or less.

The variation coefficient of diameters of the silica particles, based onvolume distribution thereof, is 23% or less. In the case where thevariation coefficient of diameters of the silica particles, based onvolume distribution thereof, is within the above described range, thesilica particles exert a spacer effect on the toner surface moreeffectively. As a result, the toner transferability is improved.Furthermore, a toner having long-term stable chargeability and fluidityis obtained. In the case where the variation coefficient of diameters ofthe silica particles is more than 23%, there are large variations involume distribution of diameters of the silica particles. Consequently,even when the volume average particle diameter (Dv) of the silicaparticles is within the above described range, the proportion ofparticles which do not function as spacer particles is large and thetoner transferability is not obtained sufficiently. Moreover, there aredifferences in properties to give the chargeability and the fluidity toa toner among individual silica particles. Consequently, the chargedistribution of the toner is extended, so that in the case where such atoner is used for image forming, fogging or the like occur easily. Thevariation coefficient of diameters of the silica particles, based onvolume distribution thereof, is preferably 15% or less, and furtherpreferably 10% or less.

Measurements of volume average particle diameter (Dv) of silicaparticles and variation coefficient of diameters of silica particles,based on volume distribution thereof.

Measurements of the volume average particle diameter (Dv) of silicaparticles and the variation coefficient of diameters of silicaparticles, based on volume distribution thereof, are performed by usingZetasizer Nano ZS (produced by SYSMEX CORPORATION). The variationcoefficient is determined in a manner as described below. Initially, thevolume distribution of the particle size is measured, so as to determinethe half-width of the volume distribution thereof and the volume averageparticle diameter (Dv). Subsequently, the ratio (%) of the half-width tothe volume average particle diameter is calculated and, thereby thevariation coefficient is determined.

Sample preparation and the measurement condition are as described below.About 1 mg of silica particles are added to 20 ml of pure water, anddispersion is performed for 3 minutes by using Homogenizer (produced bySMT). In order to reduce an influence of aggregation of silicaparticles, the volume average particle diameter (Dv) and the variationcoefficient are measured just after the dispersion under the followingcondition.

Measurement Condition

Cell: DTS0012-Disposable sizing cuvette

Dispersant: Water

Refractive index:

-   -   material: 1.460    -   dispersant: 1.330

Temperature: 25° C.

Measurement duration:

-   -   Number of runs: 5    -   Runs duration (Seconds): 10

Result Calculation General Purpose

Regarding the silica particles used in the present invention, whenheating the silica particles to measure the mass variation, the ratio ofmass decrease at the temperature in the range of 105° C. to 200° C.(hereafter may be simply referred to as ratio of mass decrease) is 0.60%or less. The ratio of mass decrease refers to the percentage of massdecrease of silica particles in the range of 105° C. to 200° C. when athermogravimetric analyzer (TGA) is used and the silica particles areheated from 50° C. to 500° C. at normal pressure. When the silicaparticles are heated, silanol groups of the silica particles aredehydrated and condensed at about 130° C. and, thereby, the mass ofsilica particles decreases. Meanwhile, water (not derived from thesilanol group), volatile substances, and the like adhering to the silicaparticles are almost volatilized at normal pressure at about 105° C.Hexamethyldisilazane (HMDS), silicone oil, and the like, which are usedas agents for treating silica, begin to volatilize at normal pressure ata temperature higher than 200° C. (about 250° C.). Consequently, thepresent inventors believe that the amount of silanol groups included inthe silica particles is quantified by measuring the ratio of massdecrease of silica particles in the range of 105° C. to 200° C.

The silanol groups of the silica particles are water-adsorption sitesand, therefore, the amount of silanol groups in the silica particlesexerts a large effect on the hygroscopicity of the silica particles.Consequently, the amount of silanol groups included in the silicaparticles exerts a large effect on the properties to give thechargeability, the fluidity, and the transferability to the toner. Inthe case where the ratio of mass decrease of the silica particles ismore than 0.60%, the amount of silanol groups in the silica particles islarge. As a result, in particular under a high-humidity environment,silica particles adsorb a large amount of water, so that the toner isnot provided with the chargeability and the fluidity sufficiently. Theratio of mass decrease of the silica particles is preferably 0.10% orless, and further preferably 0.02% or less.

Method for Measuring Ratio of Mass Decrease of Silica Particles

The ratio of mass decrease of silica particles is measured by usingHi-Res TGA 2950 Thermogravimetric Analyzer (produced by TA Instrument).About 0.03 g of silica particles serving as a sample are added to a panfor the above described analyzer, and the resulting pan is set into theanalyzer. At that time, in consideration of the bulkiness of silicaparticles, the amount of sample is adjusted appropriately. After anequilibrium state is reached at normal pressure at 50° C., that state isheld for 10 minutes, and the mass of the silica particles is measured.Subsequently, a nitrogen gas is supplied, the temperature is raised to500° C. at 20° C./min at normal pressure, and the mass variation ismeasured. Then, the percentage of the amount of mass decrease of thesilica particles in the range from 105° C. to 200° C. relative to themass of the silica particles after being held at 50° C. for 10 minutesis taken as the ratio of mass decrease.

The silica particles used in the present invention have a small ratio ofmass decrease of 0.60% or less and, therefore, the hygroscopicity isvery small as compared with that of the large-diameter silica particlesobtained by a sol-gel method in the related art. Consequently, thesurfaces thereof are not necessarily subjected to a hydrophobizingtreatment in contrast to the large-diameter silica particles obtained bythe sol-gel method in the related art. However, in order to givelong-term stable chargeability, fluidity, and transferability to thetoner, the silica particles used in the present invention may besubjected to the hydrophobizing treatment.

The method for subjecting the silica particles to the hydrophobizingtreatment is not specifically limited, and known methods may be used.Examples of methods for subjecting the silica particles to thehydrophobizing treatment include a method in which the silica particlesare treated with a hydrophobizing agent in a dry condition and a methodin which the silica particles are treated with a hydrophobizing agent ina wet condition.

Most of all, the dry hydrophobizing treatment method can be employedbecause the toner is provided with excellent fluidity while aggregationof the silica particles is prevented. Examples of dry hydrophobizingtreatment methods include a method in which the silica particles aretreated by spraying of a hydrophobizing agent under agitation and amethod in which a vapor of hydrophobizing agent is introduced to thesilica particles in a fluidized bed or under agitation.

Examples of hydrophobizing agents include the following: chlorosilanes,e.g., methyltrichlorosilane, dimethyldichlorosilane,trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane,t-butyldimethylchlorosilane, and vinyltrichlorosilane; alkoxysilanes,e.g., tetramethoxysilane, methyltrimethoxysilane,dimethyldimethoxysilane, phenyltrimethoxysilane,diphenyldimethoxysilane, o-methylphenyltrimethoxysilane,p-methylphenyltrimethoxysilane, n-butyltrimethoxysilane,i-butyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane,decyltrimethoxysilane, dodecyltrimethoxysilane, tetraethoxysilane,methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane,diphenyldiethoxysilane, i-butyltriethoxysilane, decyltriethoxysilane,vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane,γ-glycidoxypropyltrimethoxysilane,γ-glycidoxypropylmethyldimethoxysilane,γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane,γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane,γ-(2-aminoethyl)aminopropyltrimethoxysilane, andγ-(2-aminoethyl)aminopropylmethyldimethoxysilane; silazanes, e.g.,hexamethyldisilazane, hexaethyldisilazane, hexapropyldisilazane,hexabutyldisilazane, hexapentyldisilazane, hexahexyldisilazane,hexacyclohexyldisilazane, hexaphenyldisilazane,divinyltetramethyldisilazane, and dimethyltetravinyldisilazane; siliconeoils, e.g., dimethyl silicone oil, methylhydrogen silicone oil,methylphenyl silicone oil, alkyl-modified silicone oil,chloroalkyl-modified silicone oil, chlorophenyl-modified silicone oil,fatty acid-modified silicone oil, polyether-modified silicone oil,alkoxy-modified silicone oil, carbinol-modified silicone oil,amino-modified silicone oil, fluorine-modified silicone oil, andterminally-reactive silicone oil; siloxanes, e.g.,hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane,decamethylcyclopentasiloxane, hexamethyldisiloxane, andoctamethyltrisiloxane; long chain fatty acids, e.g., undecylic acid,lauric acid, tridecylic acid, dodecylic acid, myristic acid, palmiticacid, pentadecylic acid, stearic acid, heptadecylic acid, arachic acid,montanic acid, oleic acid, linoleic acid, and arachidonic acid; andsalts of the above described fatty acids and metals, e.g., zinc, iron,magnesium, aluminum, calcium, sodium, and lithium. Among them,alkoxysilanes, silazanes, and straight silicone oils can be used becausea hydrophobizing treatment is performed easily. Such hydrophobizingagents may be used alone or in combination. The above describedhydrophobizing agents may be used stepwise sequentially to surface-treatsilica particles.

In the case where the silica particles used in the present invention aresubjected to the hydrophobizing treatment, the amount of carbon derivedfrom a hydrophobizing agent in the silica particles is preferably 0.01%by mass or more and 4.5% by mass or less. In the case where the abovedescribed amount of carbon is within the above described range, theusage of the hydrophobizing agent is appropriate and degradation influidity of the silica particles is prevented. Meanwhile, as describedabove, the silica particles before being subjected to the hydrophobizingtreatment have low hygroscopicity as compared with those in the relatedart. Therefore, in order to exert this effect sufficiently, the usage ofthe hydrophobizing agent is minimized. Consequently, good chargeabilityand fluidity of the toner is enhanced. The above described amount ofcarbon is further preferably 0.02% by mass or more and 1.0% by mass orless, and particularly preferably 0.03% by mass or more and 0.08% bymass or less.

Method for Measuring Amount of Carbon of Silica Particles

The amount of carbon of the silica particles is measured by using acarbon and sulfur analyzer (EMIA-320 produced by HORIBA, Ltd.). About0.3 g of sample is precisely weighed into a crucible for the abovedescribed measurement apparatus, and 0.3 g±0.05 g of tin (Spare No.9052012500) and 1.5 g±0.1 g of tungsten (Spare No. 9051104100) are addedas fuel oil additives. Then, the silica particles are heated to 1,100°C. in an oxygen atmosphere following the description of the instructionmanual attached to the measurement apparatus. Consequently, hydrophobicgroups derived from the hydrophobizing agent on the silica particlesurfaces are thermally decomposed to CO₂. Thereafter, the amount ofcarbon contained in the silica particles is determined from the amountof the resulting CO₂ and this is taken as the amount of carbon derivedfrom the hydrophobizing agent.

Regarding the silica particles used in the present invention, the fixingratio of the hydrophobizing agent to the silica particles is preferably90% or more. In the case where the fixing ratio is within the abovedescribed range, the silica particles give good chargeability, fluidity,and transferability to the toner regardless of the environment.

Method for Measuring Fixing Ratio of Hydrophobizing Agent to SilicaParticles

The fixing ratio of the hydrophobizing agent to the silica particles ismeasured by the following method. An Erlenmeyer flask is charged with0.50 g of silica fine particles and 40 ml of chloroform and is coveredwith a lid, followed by agitation for 2 hours. Subsequently, agitationis stopped. Standing for 12 hours and centrifugal separation areperformed and a supernatant liquid is removed completely. Thecentrifugal separation is performed with Centrifuge H-9R (produced byKOKUSAN) by using Bn1 rotor and a plastic centrifuge tube for Bn1 rotorunder the condition of 20° C., 10,000 rpm, and 5 minutes.

The centrifugally separated silica particles are put into the Erlenmeyerflask again, 40 ml of chloroform is added, the lid is set, and agitationis performed for 2 hours. Subsequently, agitation is stopped. Standingfor 12 hours and centrifugal separation are performed and a supernatantliquid is removed completely. This operation is further repeated twotimes. The resulting sample is dried by using a constant temperaturebath at 50° C. for 2 hours. Furthermore, decompression to 0.07 MPa isperformed, followed by drying at 50° C. for 24 hours, so as tovolatilize chloroform sufficiently.

The amount of carbon of the silica particles treated with chloroform, asdescribed above, and the amount of carbon of the silica particles beforethe treatment with chloroform are measured following the above described“Method for measuring amount of carbon of silica particles”. The fixingratio is calculated by using a formula described below.

fixing ratio of hydrophobizing agent to the silica particles (%)=(amountof carbon of silica particles treated with chloroform/amount of carbonof silica particles)×100

The method for producing the silica particles used in the presentinvention will be described below. The method for producing the silicaparticles used in the present invention is not specifically limited.Examples thereof include the following methods: a combustion method inwhich silica particles are obtained by combustion of a silane compound(that is, a method for producing fumed silica); a deflagration method inwhich silica particles are obtained by explosive combustion of a metalsilicon powder; wet methods in which silica particles are obtained by aneutralization reaction between sodium silicate and a mineral acid(among them, synthesis under an alkaline condition is referred to as asedimentation method, and synthesis under an acid condition is referredto as a gel method); and a sol-gel method in which silica particles areobtained by hydrolysis of alkoxysilanes, e.g., hydrocarbyloxysilane (aso-called Stoeber method). Among them, the sol-gel method can beemployed as a method for producing large-diameter silica particlesbecause a sharp particle size distribution of the silica particles isobtained as compared with the other methods.

The method for producing silica particles by the sol-gel method will bedescribed below. Initially, in an organic solvent in which water ispresent, an alkoxysilane is subjected to hydrolysis and condensationreactions in the presence of a catalyst, so as to obtain a silica solsuspension liquid. The catalyst is removed from the silica solsuspension liquid, and drying is performed, so that silica particles areobtained. The silica particles obtained at this stage have silanolgroups to a large extent and are hydrophilic. Therefore, the ratio ofmass decrease takes on a value larger than 2%. In order to make theratio of mass decrease of the silica particles obtained by the abovedescribed sol-gel method fall within the range specified in the presentinvention, the silica particles are heat-treated at 300° C. to 500° C.Consequently, the silanol groups of the silica particles are dehydratedand condensed, so that the amount of silanol groups is reduced and it ispossible to reduce the value of the ratio of mass decrease of the silicaparticles.

In the case where the silica particles are treated with thehydrophobizing agent, the timing of the heat treatment at 300° C. to500° C. may be before, after, or at the same time with thehydrophobizing treatment. However, in the case where the heat treatmentis performed after the hydrophobizing treatment, the hydrophobizingagent is thermally decomposed, and the above described fixing ratio ofthe hydrophobizing agent may not be obtained. Therefore, the heattreatment can be performed before the hydrophobizing treatment.

Moreover, in order that the silica particles become monodisperse on thetoner particle surface easily and a stable spacer effect is exerted, thesilica particles can be subjected to a disintegration treatment afterbeing heat-treated. Regarding the timing of the disintegrationtreatment, the disintegration treatment can be performed before thesurface treatment is performed with the hydrophobizing agent because thesilica particle surfaces can be uniformly treated with thehydrophobizing agent.

The amount of addition (amount of external addition) of the silicaparticles used in the present invention to the toner is preferably 0.01parts by mass or more and 2.50 parts by mass or less relative to 100parts by mass of the toner particles. In the case where the amount ofaddition of the silica particles is within the above described range,the above described effects of the silica particles are exertedfavorably. The amount of addition of the silica particles to the toneris more preferably 0.10 parts by mass or more and 2.00 parts by mass orless relative to 100 parts by mass of toner particles.

The weight average particle diameter (D4) of the toner according to thepresent invention is preferably 4.0 μm or more and 9.0 μm or less, andmore preferably 5.0 μm or more and 7.5 μm or less. In the case where theweight average particle diameter (D4) of the toner is within the abovedescribed range, an occurrence of charge up is suppressed and fogging,toner scattering, and reduction in image density are prevented.

Method for Measuring Weight Average Particle Diameter (D4) and NumberAverage Particle Diameter (D1)

The weight average particle diameter (D4) and the number averageparticle diameter (D1) of the toner are calculated in a manner describedbelow. As for a measurement apparatus, a precise particle sizedistribution measurement apparatus “Coulter Counter Multisizer 3”(registered trademark, produced by Beckman Coulter, Inc.) equipped witha 100 μm aperture tube on the basis of a pore electrical resistancemethod is used. Regarding setting of the measurement conditions andanalysis of the measurement data, an attached dedicated software“Beckman Coulter Multisizer 3 Version 3.51” (produced by BeckmanCoulter, Inc.) is used. In this regard, the measurement is performedwith the number of effective measurement channels of 25,000 channels. Asfor the electrolytic aqueous solution used for the measurement, asolution prepared by dissolving special grade sodium chloride intoion-exchanged water in such a way as to have a concentration of about 1%by mass, for example, “ISOTON II” (produced by Beckman Coulter, Inc.),may be used.

By the way, prior to the measurement and the analysis, theabove-described dedicated software is set as described below. In thescreen of “Modification of the standard operating method (SOM)” of theabove-described dedicated software, the total count number in thecontrol mode is set at 50,000 particles, the number of measurements isset at 1 time, and the Kd value is set at a value obtained by using“Standard particles 10.0 μm” (produced by Beckman Coulter, Inc.). Thethreshold value and the noise level are automatically set by pressing“Threshold value/noise level measurement button”. In addition, thecurrent is set at 1,600 μA, the gain is set at 2, the electrolyticsolution is set at ISOTON II, and a check is entered in“Post-measurement aperture tube flush”. In the screen of “Setting ofconversion from pulses to particle diameter” of the above-describeddedicated software, the bin interval is set at logarithmic particlediameter, the particle diameter bin is set at 256 particle diameterbins, and the particle diameter range is set at 2 μm to 60 μm.

The specific measurement procedure is as described below.

(1) A 250 ml round-bottom glass beaker dedicated to Multisizer 3 ischarged with about 200 ml of the above-described electrolytic aqueoussolution, the beaker is set in a sample stand, and counterclockwiseagitation is performed with a stirrer rod at 24 revolutions/sec. Then,contamination and air bubbles in the aperture tube are removed by“Aperture flush” function of the dedicated software.(2) A 100 ml flat-bottom glass beaker is charged with about 30 ml of theabove-described electrolytic aqueous solution. A diluted solution isprepared by diluting “Contaminon N” (a 10% by mass aqueous solution ofneutral detergent for washing a precision measuring device, including anonionic surfactant, an anionic surfactant, and an organic builder andhaving a pH of 7, produced by Wako Pure Chemical Industries, Ltd.) withion-exchanged water by a factor of about 3 on a mass basis and about 0.3ml of the diluted solution serving as a dispersing agent is added to theinside of the beaker.(3) An ultrasonic dispersing machine “Ultrasonic Dispersion SystemTetora 150” (produced by Nikkaki Bios Co., Ltd.) is prepared, the systemincorporating two oscillators with an oscillatory frequency of 50 kHz insuch a way that the phases are displaced by 180 degrees and having anelectrical output of 120 W. Then, about 3.3 l of ion-exchanged water isput into a water tank of the ultrasonic dispersion system, and about 2ml of Contaminon N is added to the inside of this water tank.(4) The beaker in the above-described item (2) is set in a beaker fixinghole of the above-described ultrasonic dispersion system, and theultrasonic dispersion system is actuated. The height position of thebeaker is adjusted in such a way that the resonance state of the liquidsurface of the electrolytic aqueous solution in the beaker is maximized.(5) Ultrasonic waves are applied to the electrolytic aqueous solution inthe beaker of the above-described item (4). In this state, about 10 mgof toner is added to the above-described electrolytic aqueous solutionlittle by little and is dispersed. Subsequently, an ultrasonicdispersion treatment is further continued for 60 seconds. In thisregard, in the ultrasonic dispersion, the water temperature of the watertank is controlled at 10° C. or higher and 40° C. or lowerappropriately.(6) The electrolytic aqueous solution, in which the toner is dispersed,of the above-described item (5) is dropped to the round-bottom beaker ofthe above-described item (1) set in the sample stand by using a pipettein such a way that the measurement concentration is adjusted to becomeabout 5%. Then, the measurement is performed until the number ofmeasured particles reaches 50,000.(7) The measurement data are analyzed by the above-described dedicatedsoftware attached to the apparatus, so that the weight average particlediameter (D4) and the number average particle diameter (D1) arecalculated. In this regard, when Graph/% by volume is set in theabove-described dedicated software, “Average diameter” on the screen of“Analysis/statistical value on volume (arithmetic average)” is theweight average particle diameter (D4), and when Graph/% by the number isset in the above-described dedicated software, “Average diameter” on thescreen of “Analysis/statistical value on the number (arithmeticaverage)” is the number average particle diameter (D1).

The toner according to the present invention can contain at least onetype of wax. The total amount of waxes contained in the toner ispreferably 2.5 parts by mass or more and 25.0 parts by mass or lessrelative to 100 parts by mass of the toner particles. The total amountof waxes contained in the toner particles is preferably 4.0 parts bymass or more and 20 parts by mass or less, and further preferably 6.0parts by mass or more and 18.0 parts by mass or less. In the case wherethe amount of wax is 2.5 parts by mass or more and 25.0 parts by mass orless, an appropriate bleeding property of wax is ensured during heatingand pressurizing of the toner, so that winding resistance is improved.Furthermore, even when the toner undergoes a stress during developmentor transfer, exposure of wax at the toner surface is at a low level andindividual toner particles obtain nearly uniform triboelectricchargeability. Examples of waxes include the following: aliphatichydrocarbon based waxes, e.g., low-molecular weight polyethylene,low-molecular weight polypropylene, microcrystalline waxes,Fischer-Tropsch waxes, and paraffin waxes; oxides of aliphatichydrocarbon based waxes, e.g., oxidized polyethylene wax, or blockcopolymers thereof; waxes containing a fatty acid ester as a primarycomponent, e.g., carnauba wax and montanic acid ester wax, and waxesproduced by partly or wholly deacidifying fatty acid esters, e.g.,deacidified carnauba wax; saturated straight chain fatty acids, e.g.,palmitic acid, stearic acid, and montanic acid; unsaturated fatty acids,e.g., brassidic acid, eleostearic acid, and parinaric acid; saturatedalcohols, e.g., stearyl alcohol, aralkyl alcohol, behenyl alcohol,carnaubyl alcohol, ceryl alcohol, and melissyl alcohol; polyhydricalcohols, e.g., sorbitol; fatty acid amides, e.g., linolamide, oleamide,and lauramide; saturated fatty acid bis-amides, e.g.,methylene-bis-stearamide, ethylene-bis-capramide,ethylene-bis-lauramide, and hexamethylene-bis-stearamide; unsaturatedfatty acid amides, e.g., ethylene-bis-oleamide,hexamethylene-bis-oleamide, N,N′-dioleyl adipamide, and N,N′-dioleylsebacamide; aromatic bisamides, e.g., m-xylene-bis-stearamide, andN,N′-distearyl isophthalamide; aliphatic metal salts (those generallyreferred to as metallic soaps), e.g., calcium stearate, calcium laurate,zinc stearate, and magnesium stearate; waxes which are aliphatichydrocarbon based waxes grafted by using vinyl based monomers, e.g.,styrene and acrylic acid; partly esterified products of fatty acids andpolyhydric alcohols, e.g., behenic monoglyceride; and methyl estercompounds which are obtained by hydrogenation of vegetable oils and fatsand which have hydroxyl groups.

Examples of binder resins of the toner include the following:polystyrenes; homopolymers of styrene substitution products, e.g.,poly-p-chlorostyrene and polyvinyltoluene; styrene based copolymers,e.g., styrene-p-chlorostyrene copolymers, styrene-vinyltoluenecopolymers, styrene-vinylnaphthalene copolymers, styrene-acrylic acidester copolymers, styrene-methacrylic acid ester copolymers,styrene-methyl α-chloromethacrylate copolymers, styrene-acrylonitrilecopolymers, styrene-vinyl methyl ether copolymers, styrene-vinyl ethylether copolymers, styrene-vinyl methyl ketone copolymers,styrene-butadiene copolymers, styrene-isoprene copolymers, andstyrene-acrylonitrile-indene copolymers; acrylic resins; methacrylicresins; polyvinyl acetate; silicone resins; polyester resins; polyamideresins; furan resins; epoxy resins; and xylene resins. These resins maybe used alone or in combination.

The toner particles used in the present invention may be produced byusing a known pulverization method or polymerization method. Inparticular, the polymerization method can be employed because tonerparticles which are close to a sphere and which have surfaces with a lowlevel of unevenness are obtained as compared with the pulverizationmethod and, thereby the effect of giving the transferability is exertedby the silica particles synergetically. Among the polymerizationmethods, in particular, toner particles can be obtained by a suspensionpolymerization method.

The method for producing toner particles by the suspensionpolymerization method will be described below. A polymerizable monomercomposition containing a polymerizable monomer, a colorant, a wax, otheradditives as necessary, and the like is dissolved or dispersed with adispersing machine, e.g., a homogenizer, a ball mill, a colloid mill, oran ultrasonic dispersing machine, so as to be suspended in an aqueousmedium containing a dispersion stabilizer. A polymerization initiator isused and the polymerizable monomer in the polymerizable monomercomposition is polymerized, so as to produce toner particles. Thepolymerization initiator may be added at the same time as addition ofthe other additives to the polymerizable monomer, or be mixed justbefore the polymerizable monomer composition is suspended in the aqueousmedium. Alternatively, the polymerization initiator dissolved into thepolymerizable monomer or the solvent may be added just after granulationis completed and before the polymerization reaction is initiated.

As for the polymerizable monomer, a vinyl based polymerizable monomercapable of being radically polymerized is used. As for the vinyl basedpolymerizable monomer, a monofunctional monomer or a polyfunctionalmonomer may be used. Examples of monofunctional polymerizable monomersinclude the following: styrene; styrene derivatives, e.g., α-methylstyrene, β-methyl styrene, o-methyl styrene, m-methyl styrene, p-methylstyrene, 2,4-dimethyl styrene, p-n-butyl styrene, p-tert-butyl styrene,p-n-hexyl styrene, p-n-octyl styrene, p-n-nonyl styrene, p-n-decylstyrene, p-n-dodecyl styrene, p-methoxy styrene, and p-phenyl styrene;acrylic polymerizable monomers, e.g., methyl acrylate, ethyl acrylate,n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butylacrylate, tert-butyl acrylate, n-amyl acrylate, n-hexyl acrylate,2-ethylhexyl acrylate, n-octyl acrylate, n-nonyl acrylate, cyclohexylacrylate, benzyl acrylate, dimethyl phosphate ethyl acrylate, diethylphosphate ethyl acrylate, dibutyl phosphate ethyl acrylate, and2-benzoyloxy ethyl acrylate; methacrylic polymerizable monomers, e.g.,methyl methacrylate, ethyl methacrylate, n-propyl methacrylate,iso-propyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate,tert-butyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate,2-ethylhexyl methacrylate, n-octyl methacrylate, n-nonyl methacrylate,diethyl phosphate ethyl methacrylate, and dibutyl phosphate ethylmethacrylate; methylene aliphatic monocarboxylic acid ester; vinylesters, e.g., vinyl acetate, vinyl propionate, vinyl butyrate, vinylbenzoate, and vinyl formate; vinyl ethers, e.g., vinyl methyl ether,vinyl ethyl ether, and vinyl isobutyl ether; and vinyl ketones, e.g.,vinyl methyl ketone, vinyl hexyl ketone, and vinyl isopropyl ketone.

Examples of polyfunctional polymerizable monomers include the following:diethylene glycol diacrylate, triethylene glycol diacrylate,tetraethylene glycol diacrylate, polyethylene glycol diacrylate,1,6-hexane diol diacrylate, neopentyl glycol diacrylate, tripropyleneglycol diacrylate, polypropylene glycol diacrylate,2,2′-bis(4-(acryloxy•diethoxy)phenyl)propane, trimethylolpropanetriacrylate, tetramethylolmethane tetraacrylate, ethylene glycoldimethacrylate, diethylene glycol dimethacrylate, triethylene glycoldimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycoldimethacrylate, 1,3-butylene glycol dimethacrylate, 1,6-hexane dioldimethacrylate, neopentyl glycol dimethacrylate, polypropylene glycoldimethacrylate, 2,2′-bis(4-(methacryloxy•diethoxy)phenyl)propane,2,2′-bis(4-(methacryloxy•polyethoxy)phenyl)propane, trimethylolpropanetrimethacrylate, tetramethylolmethane tetramethacrylate, divinylbenzene,divinylnaphthalene, and divinyl ether.

The monofunctional polymerizable monomers are used alone, in combinationof at least two types, or in combination with the polyfunctionalpolymerizable monomers. The polyfunctional polymerizable monomer mayalso be used as a cross-linking agent.

As for the polymerization initiator used in polymerization of thepolymerizable monomer, oil-soluble initiators and/or water-solubleinitiators are used. Examples of oil-soluble initiators include thefollowing: azo compounds, e.g., 2,2′-azobisisobutyronitrile,2,2′-azobis-2,4-dimethylvaleronitrile,1,1′-azobis(cyclohexane-1-carbonitrile), and2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile; and peroxide basedinitiators, e.g., acetylcyclohexylsulfonyl peroxide, diisopropylperoxycarbonate, decanonyl peroxide, lauroyl peroxide, stearoylperoxide, propionyl peroxide, acetyl peroxide, t-butylperoxy-2-ethylhexanoate, benzoyl peroxide, t-butyl peroxyisobutyrate,cyclohexanone peroxide, methyl ethyl ketone peroxide, dicumyl peroxide,t-butyl hydroperoxide, di-t-butyl peroxide, and cumene hydroperoxide.Examples of water-soluble initiators include the following: ammoniumpersulfate, potassium persulfate, 2,2′-azobis(N,N′-dimethylene isobutylamidine) hydrochloride, 2,2′-azobis(2-aminodinopropane) hydrochloride,azobis(isobutyl amidine) hydrochloride, sodium2,2′-azobisisobutyronitrile sulfonate, ferrous sulfate, and hydrogenperoxide. Furthermore, a chain transfer agent, a polymerizationinhibitor, and the like may be used in order to control the degree ofpolymerization of the polymerizable monomer.

As for the cross-linking agent, a compound having at least twopolymerizable double bonds is used. Specific examples thereof includearomatic divinyl compounds; e.g., divinylbenzene and divinylnaphthalene;carboxylic acid esters having two double bonds, e.g., ethylene glycoldiacrylate, ethylene glycol dimethacrylate, and 1,3-butane dioldimethacrylate; divinyl compounds, e.g., divinylaniline, divinyl ether,divinyl sulfide, and divinyl sulfone; and compounds having at leastthree vinyl groups. They are used alone or as a mixture.

As for the colorant, black, yellow, magenta, and cyan colorants,described below, may be used.

As for the black colorant, carbon black and magnetic substances may beused. Furthermore, a color and a toner resistance may be adjusted bymixing the following coloring materials.

As for pigment based yellow colorants, compounds typified by condensedazo compounds, isoindolinone compounds, anthraquinone compounds, azometal complex methine compounds, and allylamide compounds are used.Specific examples include C. I. Pigment Yellow 3, 7, 10, 12, 13, 14, 15,17, 23, 24, 60, 62, 74, 75, 83, 93, 94, 95, 99, 100, 101, 104, 108, 109,110, 111, 117, 123, 128, 129, 138, 139, 147, 148, 150, 155, 166, 168,169, 177, 179, 180, 181, 183, 185, 191:1, 191, 192, 193, and 199.Examples of die based yellow colorants include C. I. solvent Yellow 33,56, 79, 82, 93, 112, 162, and 163, and C. I. disperse Yellow 42, 64,201, and 211.

As for magenta colorants, condensed azo compounds, diketopyrrolopyrrolecompounds, anthraquinone, quinacridone compounds, basic dye lakecompounds, naphthol compounds, benzimidazolone compounds, thioindigocompounds, and perylene compounds are used. Specific examples include C.I. Pigment Red 2, 3, 5, 6, 7, 23, 48:2, 48:3, 48:4, 57:1, 81:1, 122,146, 166, 169, 177, 184, 185, 202, 206, 220, 221, 238, 254, and 269 andC. I. Pigment Violet 19.

As for cyan colorants, phthalocyanine compounds and derivatives thereof,anthraquinone compounds, and basic dye lake compounds are used. Specificexamples include C. I. Pigment Blue 1, 7, 15, 15:1, 15:2, 15:3, 15:4,60, 62, and 66.

These colorants may be used alone or in combination. Furthermore, thecolorant may be used in the state of solid solution. The colorant isselected from the viewpoint of the hue angle, the saturation, thebrightness, the weather resistance, the OHP transparency, anddispersibility into the toner. The amount of addition of the colorant ispreferably 1 part by mass or more and 20 parts by mass or less relativeto 100 parts by mass of binder resin.

In order to keep the stable chargeability of the toner, a charge controlagent can be applied to the toner. Examples of negative charge controlagents include the following: monoazo metal compounds; acetylacetonemetal compounds; aromatic oxycarboxylic acids, aromatic dicarboxylicacids, oxycarboxylic acids, dicarboxylic acids, and metal compounds,anhydrides, and ester compounds of these acids; phenol derivatives,e.g., bisphenol; urea derivatives; metal-containing salicylic acid basedcompounds; metal-containing naphthoic acid based compounds; boroncompounds; quaternary ammonium salts; calixarenes; and resin basedcharge control agents. Examples of positive charge control agentsinclude the following: nigrosine-modified compounds on the basis ofnigrosine, fatty acid metal salts, and the like; guanidine compounds,imidazole compounds,tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, quaternary ammoniumsalts, e.g., tetrabutylammonium tetrafluoroborate, onium salts which areanalogues thereof, e.g., phosphonium salts, and lake pigments thereof;triphenylmethane dyes and lake pigments thereof (examples of lakingagents include phosphotungstic acid, phosphomolybdic acid,phosphotungsten molybdic acid, tannic acid, lauric acid, gallic acid,ferricyanides, and ferrocyanides); metal salts of higher fatty acids;diorganotin oxides, e.g., dibutyltin oxide, dioctyltin oxide, anddicyclohexyltin oxide; diorganotin borates, e.g., dibutyltin borate,dioctyltin borate, and dicyclohexyltin borate; and resin based chargecontrol agents. They may be used alone or in combination.

Most of all, salicylic acid based metal compounds can be used as thecharge control agent, and furthermore, aluminum or zirconium can beemployed as the metal thereof. In particular, aluminum salicylatecompounds can be used as the charge control agent. The content of thecharge control agent is preferably 0.01 parts by mass or more and 20.00parts by mass or less relative to 100 parts by mass of binder resin, andmore preferably 0.50 parts by mass or more and 10.00 parts by mass orless.

Besides the above described silica particles, other inorganic finepowders can be externally added in order to improve the chargestability, developability, the fluidity, the transferability, and thelike. Examples of other fine particles include metal oxides, e.g.,silica, alumina, and titania, and compound oxides thereof andfluorocarbon. At least two types of them may be used in combination. Inparticular, silica, alumina, titania, and compound oxides thereof can beused because the fluidity and the chargeability of the toner aremaintained favorably and adsorption performance with respect to tonerparticles is high.

The inorganic fine powder used besides the above described silicaparticles has an average primary particle diameter of preferably 5 nm ormore and 70 nm or less. In the case where the average primary particlediameter of the inorganic fine powder is within the above describedrange, good fluidity and chargeability of the toner can be maintainedover a long term.

Method for Measuring Average Primary Particle Diameter of Inorganic FinePowder

Regarding the average primary particle diameter of the inorganic finepowder, the inorganic fine powder is observed with a transmissionelectron microscope, and in a field of view magnified by 30,000 to50,000 times, an average value of major axes of 300 primary particleshaving major axes of 1 nm or more is calculated. In this regard, in thecase where sampled particles are small in such a way that the particlediameter cannot be measured under a magnification of 50,000 times, thephotograph is further magnified in such a way that the primary diametersbecome 5 mm or more, and the measurement is performed.

The inorganic fine powder can be subjected to a hydrophobizingtreatment. The hydrophobizing treatment method and the hydrophobizingagent are the same as those in the case where the above described silicaparticles are subjected to the hydrophobizing treatment.

The total amount of the silica particles and the inorganic fine powderadded to the toner is preferably 0.5 parts by mass or more and 4.5 partsby mass or less, and more preferably 0.8 parts by mass or more and 3.5parts by mass or less relative to 100 parts by mass of toner particles.In the case where the total amount of the silica particles and theinorganic fine powder is within the above described range, the fluidityof the toner is obtained sufficiently, degradation in fogging and tonerscattering associated with reduction in chargeability of the toner canbe prevented.

Known external additives, e.g., charge control particles, an abrasive,and a caking inhibitor, may be used besides the inorganic fine powder.Examples of charge control particles include metal oxides (tin oxide,titania, zinc oxide, alumina, antimony oxide, and the like) and carbonblack. Examples of abrasives include metal oxides (strontium titanate,cerium oxide, aluminum oxide, magnesium oxide, chromium oxide, and thelike), nitrides (silicon nitride and the like), carbides (siliconcarbide and the like), and meal salts (calcium sulfate, barium sulfate,calcium carbonate, and the like).

Furthermore, a lubricant may also be used in order to reducecontamination of the members. Examples of lubricants include fluorinebased resin powders (polyvinylidene fluoride, polytetrafluoroethylene,and the like) and fatty acid metal salts (zinc stearate, calciumstearate, and the like). Among those described above, zinc stearate canbe used. The amount of addition of these charge control particles,abrasive, caking inhibitor, and the like (excluding the silica particlesand the above described inorganic fine powder) is preferably 0.01 partsby mass or more and 2.50 parts by mass or less, and more preferably 0.10parts by mass or more and 2.00 parts by mass or less relative to 100parts by mass of toner particles.

The toner according to the present invention may be used for any one ofa high-speed system, oilless fixing, a cleaner-less system, and adeveloping system in which carriers degraded through a long term of usein a developing device are recovered sequentially and fresh carriers aresupplied. Moreover, the toner can be applied to known image formingmethods by using a one-component developing system or a two-componentdeveloping system. In particular, the toner according to the presentinvention has very good transferability and, therefore, can be used inan image forming method including an intermediate transfer body and animage forming method including a cleaner-less system regardless of theone-component developing system or the two-component developing system.

The toner according to the present invention may be used as atwo-component system developing agent with respect to either full coloror monochrome.

EXAMPLES Production Example of Silica Particles 1

A 3-liter glass reactor provided with an agitator, a dropping funnel,and a thermometer was charged with 589.6 g of methanol, 42.0 g of water,and 47.1 g of 28% by mass ammonia water, followed by mixing. Theresulting solution was adjusted to become 35° C., and addition of1,100.0 g (7.23 mol) of tetramethoxysilane and 395.2 g of 5.4% by massammonia water was started at the same time under agitation.Tetramethoxysilane was dropped over 6 hours and ammonia water wasdropped over 5 hours. After the dropping was completed, agitation wascontinued for further 0.5 hours to effect hydrolysis, so that amethanol-water dispersion liquid of hydrophilic spherical sol-gel silicafine particles was obtained. Subsequently, an ester adaptor and acooling tube were attached to the glass reactor and the above describeddispersion liquid was dried at 80° C. under reduced pressuresufficiently. The resulting silica particles were heated in a constanttemperature bath at 400° C. for 10 minutes.

The above described step was performed several tens of times, and theresulting silica particles were subjected to a disintegration treatmentwith Pulverizer (produced by Hosokawa Micron Corporation).

Thereafter, 500 g of silica particles were charged into apolytetrafluoroethylene internal cylinder type stainless steel autoclavehaving an internal volume of 1,000 ml. The inside of the autoclave wassubstituted with nitrogen and, then, 0.5 g of hexamethyldisilazane(HMDS) and 0.1 g of water made into a fog with a two-fluid nozzle wereblown on the silica particles uniformly while an agitation bladeattached to the autoclave was rotated at 400 rpm. After agitation wasperformed for 30 minutes, the autoclave was sealed and heated at 200° C.for 2 hours. Subsequently, the inside of the system was decompressedwhile heating was continued, so that a deammoniation treatment wasperformed to obtain Silica particles 1. The properties of Silicaparticles 1 are shown in Table 1.

Production Examples of Silica Particles 2 to 4

Regarding the production example of Silica particles 1, the amount ofmethanol used at an initial stage was changed to 530.6 g, 634.0 g, and737.3 g, respectively. Furthermore, the dropping time oftetramethoxysilane was changed to 7 hours, 6 hours, and 5 hours,respectively, and the dropping time of the 5.4% by mass ammonia waterwas changed to 6 hours, 5 hours, and 4 hours, respectively. The volumeaverage particle diameter (Dv) of the silica particles and the variationcoefficient of diameters of the silica particles, based on volumedistribution thereof, were adjusted by the above described operation.Moreover, in the surface treatment with HMDS, the amounts of HMDS andwater were adjusted in such a way that the amount of carbon became thesame as the amount of Silica particles 1 and, thereby, Silica particles2 to 4 were obtained. The properties of Silica particles 2 to 4 areshown in Table 1.

Production Examples of Silica Particles 5 to 7

Regarding the production example of Silica particles 1, the amount ofmethanol used at an initial stage was changed to 491.3 g, 360.1 g, and294.8 g, respectively. Furthermore, the dropping time oftetramethoxysilane was changed to 7 hours, 5.5 hours, and 5 hours,respectively, and the dropping time of the 5.4% by mass ammonia waterwas changed to 6 hours, 4.5 hours, and 4 hours, respectively. The volumeaverage particle diameter (Dv) of the silica particles and the variationcoefficient of diameters of the silica particles, based on volumedistribution thereof, were adjusted by the above described operation.Moreover, in the surface treatment with HMDS, the amounts of HMDS andwater were adjusted in such a way that the amount of carbon became thesame as the amount of Silica particles 1 and, thereby, Silica particles5 to 7 were obtained. The properties of Silica particles 5 to 7 areshown in Table 1.

Production Examples of Silica Particles 8 to 11

Regarding the production example of Silica particles 1, the droppingtime of tetramethoxysilane was changed to 6 hours, 5 hours, 3.5 hours,and 2 hours, respectively, and the dropping time of the 5.4% by massammonia water was changed to 5 hours, 4 hours, 3 hours, and 2 hours,respectively. The volume average particle diameter (Dv) of the silicaparticles and the variation coefficient of diameters of the silicaparticles, based on volume distribution thereof, were adjusted by theabove described operation. Moreover, in the surface treatment with HMDS,the amounts of HMDS and water were adjusted in such a way that theamount of carbon became the same as the amount of Silica particles 1and, thereby, Silica particles 8 to 11 were obtained. The properties ofSilica particles 8 to 11 are shown in Table 1.

Production Examples of Silica Particles 12 to 15

Regarding the production example of Silica particles 1, the time ofheating in the constant temperature bath at 400° C. was changed to 9minutes, 8 minutes, 3.2 minutes, and 1.4 minutes, respectively. Theratio of mass decrease when heating from 105° C. to 200° C. wasperformed was adjusted and, thereby, Silica particles 12 to 15 wereobtained. The properties of Silica particles 12 to 15 are shown in Table1.

Production Example of Silica Particles 16

Silica particles (fumed silica) having a volume average particlediameter (Dv) of 92 nm were produced by a combustion method. Thevariation coefficient of diameters of the silica particles, based onvolume distribution thereof, was 35%. The particles were classified and,thereby, silica particles having a volume average particle diameter (Dv)of 85 nm and a variation coefficient of diameters of particles, based onvolume distribution thereof, of 21% were obtained. The particles weresurface-treated with HMDS in the same manner as that for Silicaparticles 1, so as to obtain Silica particles 16. The properties ofSilica particles 16 are shown in Table 1.

Production Example of Silica Particles 17

Silica particles having a volume average particle diameter (Dv) of 150nm ware produced from metal silicon serving as a raw material throughdeflagration on the basis of the method described in Japanese PatentLaid-Open No. 60-255602. The variation coefficient of diameters of thesilica particles, based on volume distribution thereof, was 30%. Theparticles were classified and, thereby, silica particles having a volumeaverage particle diameter (Dv) of 120 nm and a variation coefficient ofdiameters of particles, based on volume distribution thereof, of 21%were obtained. The particles were surface-treated with HMDS in the samemanner as that for Silica particles 1, so as to obtain Silica particles17. The properties of Silica particles 17 are shown in Table 1.

Production Examples of Silica Particles 18 and 19

Regarding the production example of Silica particles 1, the heatingtemperature in the surface treatment with HMDS was adjusted in such away that the fixing ratio became 90% and 86%, respectively, so as toobtain Silica particles 18 and 19. The properties of Silica particles 18and 19 are shown in Table 1.

Production Example of Silica Particles 20

Regarding the production example of Silica particles 1, the amounts ofHMDS and water in the surface treatment with HMDS were changed to 0.80 gand 0.15 g, respectively, so as to obtain Silica particles 20. Theproperties of Silica particles 20 are shown in Table 1.

Production Example of Silica Particles 21

Regarding the production example of Silica particles 1, the amounts ofHMDS and water in the surface treatment with HMDS were changed to 10.00g and 1.50 g, respectively, so as to obtain Silica particles 21. Theproperties of Silica particles 21 are shown in Table 1.

Production Example of Silica Particles 22

Regarding the production example of Silica particles 1, the amounts ofHMDS and water in the surface treatment with HMDS were changed to 50.00g and 7.50 g, respectively, so as to obtain Silica particles 22. Theproperties of Silica particles 22 are shown in Table 1.

Production Example of Silica Particles 23

Regarding the production example of Silica particles 1, the amounts ofHMDS and water in the surface treatment with HMDS were changed to 65.00g and 9.50 g, respectively, so as to obtain Silica particles 23. Theproperties of Silica particles 23 are shown in Table 1.

Production Example of Silica Particles 24

Regarding the production example of Silica particles 1, the surfacetreatment with HMDS was not performed and the time of heating in theconstant temperature bath at 400° C. was changed to 15 minutes. Silicaparticles 24 were obtained as in the production example of Silicaparticles 1 except those described above. The properties of Silicaparticles 24 are shown in Table 1.

TABLE 1 Volume Variation coefficient of average diameter of particles,Ratio of Fixing ratio of Amount of Silica particle based on volume massProduction hydrophobizing carbon (% particles diameter (nm) distribution(%) decrease (%) method agent (%) by mass) Silica 100 9 0.01 sol-gel 950.05 particles 1 method Silica 80 9 0.01 sol-gel 94 0.05 particles 2method Silica 70 10 0.01 sol-gel 93 0.05 particles 3 method Silica 60 180.01 sol-gel 94 0.05 particles 4 method Silica 200 9 0.01 sol-gel 950.05 particles 5 method Silica 500 13 0.01 sol-gel 93 0.05 particles 6method Silica 600 21 0.01 sol-gel 92 0.05 particles 7 method Silica 10010 0.01 sol-gel 94 0.05 particles 8 method Silica 190 15 0.01 sol-gel 950.05 particles 9 method Silica 200 23 0.01 sol-gel 95 0.05 particles 10method Silica 200 27 0.01 sol-gel 92 0.05 particles 11 method Silica 1009 0.02 sol-gel 91 0.05 particles 12 method Silica 100 9 0.10 sol-gel 930.05 particles 13 method Silica 100 9 0.60 sol-gel 95 0.05 particles 14method Silica 100 9 0.90 sol-gel 94 0.05 particles 15 method Silica 8521 0.14 fuming 91 0.05 particles 16 method Silica 120 21 0.06deflagration 91 0.05 particles 17 method Silica 100 9 0.01 sol-gel 900.05 particles 18 method Silica 100 9 0.01 sol-gel 86 0.05 particles 19method Silica 100 9 0.01 sol-gel 93 0.08 particles 20 method Silica 1009 0.01 sol-gel 91 1.0 particles 21 method Silica 100 9 0.01 sol-gel 914.5 particles 22 method Silica 100 9 0.01 sol-gel 90 6.2 particles 23method Silica 100 9 0 sol-gel untreated — particles 24 method

Production Example of Charge Control Resin 1

A pressurizable reaction container provided with a reflux tube, anagitator, a thermometer, a nitrogen introduction tube, a droppingdevice, and a decompression device is charged with 250 parts by mass ofmethanol, 150 parts by mass of 2-butanone, and 100 parts by mass of2-propanol, which are solvents, and 77 parts by mass of styrene, 15parts by mass of 2-ethylhexyl acrylate, and 8 parts by mass of2-acrylamide-2-methylpropane sulfonic acid, which are monomers, and washeated to a reflux temperature under agitation. A solution, in which 1part by mass of t-butylperoxy-2-ethylhexanoate serving as apolymerization initiator was diluted with 20 parts by mass of2-butanone, was dropped over 30 minutes and agitation was continued for5 hours. Furthermore, the solution, in which 1 part by mass oft-butylperoxy-2-ethylhexanoate was diluted with 20 parts by mass of2-butanone, was dropped over 30 minutes, agitation was performed for 5hours, and polymerization was terminated. While the temperature wasmaintained, 500 parts by mass of deionized water was added, andagitation was performed at 80 to 100 revolutions per minute for 2 hoursin such a way that the interface between an organic layer and a waterlayer was not disturbed. After the layers were separated by being stoodfor 30 minutes, the water layer was removed, and anhydrous sodiumsulfate was added to the organic layer, so as to dehydrate.Subsequently, the polymerization solvents were removed throughdistillation under reduced pressure, and the resulting polymer wascoarsely pulverized into 100 μm or less by using a cutter mill equippedwith a 150 mesh screen. The resulting Charge control resin 1 containinga sulfur atom had Tg of 58° C., Mp of 13,000, and Mw of 30,000.

Production Example of Toner Particles 1

With respect to 100 parts by mass of styrene monomer, 16.5 parts by massof C. I. Pigment Blue 15:3 and 3.0 parts by mass of aluminum compound ofdi-tert-butylsalicylic acid (Bontron E-88 produced by Orient ChemicalIndustries, Ltd.) were prepared. They were introduced into an attritor(produced by MITSUI MINING COMPANY, LIMITED), and agitation wasperformed at 25° C. for 180 minutes by using zirconia beads having aradius of 1.25 mm (140 parts by mass) at 200 rpm, so that Master batchdispersion liquid 1 was prepared.

Meanwhile, 450 parts by mass of 0.1 M-Na₃PO₄ aqueous solution was putinto 710 parts by mass of ion-exchanged water, the temperature wasraised to 60° C., and 67.7 parts by mass of 1.0 M-CaCl₂ aqueous solutionwas added gradually, so that an aqueous medium containing a calciumphosphate compound was obtained.

Master batch dispersion liquid 1  40 parts by mass Styrene monomer  28parts by mass n-Butyl acrylate monomer  18 parts by mass Low-molecularweight polystyrene  20 parts by mass (Mw = 3,000, Mn = 1,050, Tg = 55°C.) Hydrocarbon based wax   9 parts by mass (Fischer-Tropsch wax, peaktemperature of maximum endothermic peak = 78° C., Mw = 750) Chargecontrol resin 1 0.3 parts by mass Polyester resin   5 parts by mass

(Polycondensate of terephthalic acid:isophthalic acid: propyleneoxide-modified bisphenol A (2 mol adduct):ethylene oxide-modifiedbisphenol A (2 mol adduct)=30:30:30:10, acid value 11 mgKOH/g, Tg=74°C., Mw=11,000, Mn=4,000)

The above described materials were heated to 65° C., and were dissolvedand dispersed homogeneously with TK type Homomixer (produced by TokushuKika Kogyou Co., Ltd.) at 5,000 rpm. A polymerizable monomer compositionwas prepared by dissolving 7.1 parts by mass of 70% toluene solution of1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate serving as apolymerization initiator into the dispersion liquid.

The above described polymerizable monomer composition was put into theabove described aqueous medium, and agitation was performed at atemperature of 65° C. for 10 minutes in a N₂ atmosphere with TK typeHomomixer at 10,000 rpm, so as to granulate the polymerizable monomercomposition. Thereafter, the temperature was raised to 67° C. whileagitation was performed with a paddle agitation blade, and when thedegree of polymerization conversion of the polymerizable vinyl basedmonomer reached 90%, 0.1 mol/l sodium hydroxide aqueous solution wasadded to adjust the pH of the aqueous dispersion medium to 9.Furthermore, the temperature was raised to 80° C. at a temperatureincrease rate of 40° C./h and the reaction was effected for 4 hours.After the polymerization was terminated, remaining monomers of tonerparticles for supply were removed through distillation under reducedpressure. The aqueous medium was cooled and, subsequently, hydrochloricacid was added to adjust the pH to 1.4, and calcium phosphate wasdissolved by performing agitation for 6 hours. Toner particles wereseparated through filtration and were washed with water. Then, dryingwas performed at a temperature of 40° C. for 48 hours. Regarding theresulting dried product, ultrafine powders and coarse powders wereprecisely classified and removed with a multi-division classifier(Elbow-Jet Classifier produced by Nittetsu Mining Co., Ltd.) at the sametime, so that cyan Toner particles 1 having a weight average particlediameter (D4) of 6.3 μm was obtained.

Example 1

Toner 1 was obtained by dry-mixing 1.5 parts by mass of Silica particles1 and 0.2 parts by mass of rutile-type titanium dioxide fine powdersurface-treated with dimethyl silicone oil (average primary particlediameter: 30 nm) relative to 100 parts by mass of Toner particles 1 for5 minutes with Henschel mixer (produced by MITSUI MINING COMPANY,LIMITED). Then, Toner 1 was evaluated as described below. The evaluationresults are shown in Table 2.

Image Output Test

A printer LBP-7200C produced by CANON KABUSHIKI KAISHA was used, andimages were evaluated in various environments. In this regard, LBP 7200Cis a system which does not have a cleaning member in an intermediatetransfer unit portion and which recovers remaining toners of primary andsecondary transfer with a cleaning member in a photo conductor unit. Acartridge filled with 70 g of Toner 1 was mounted on the cyan station ofthe above described printer, dummy cartridges were mounted on otherstations, and an image output test was performed.

Images were evaluated in each of environments of 15° C./10% Rh(low-temperature low-humidity environment) and 32.5° C./90% Rh(high-temperature high-humidity environment). In each environment, anoperation to output an image with a coverage of 1% was repeated, andevery time the number of the output sheets reached 200, standing wasperformed for a week in each environment. Thereafter, the step to output200 sheets in the above described manner was repeated, and finally 4,600sheets were output. Then, an evaluation was performed by a method asdescribed below.

(1) Evaluation of Fogging

In the above described image output test, every time after standing fora week, one sheet of image having a white background portion was output.Subsequently, regarding every image having a white background portion,the fogging concentration (%) (=Dr (%)−Ds (%)) was calculated from thedifference between the degree of whiteness (reflectance Ds (%)) of thewhite background portion of the image having a white background portionand the degree of whiteness (average reflectance Dr (%)) of transferpaper. In this regard, the degree of whiteness was measured with“REFLECTMETER MODEL TC-6DS” (produced by Tokyo Denshoku Co., Ltd.). Asfor the filter, the Amberlite filter was used. The foggingconcentrations were ranked as described below. A, B, and C areacceptable levels in the present invention.

A: The fogging concentration is less than 0.3%.B: The fogging concentration is 0.3% or more and less than 0.8%.C: The fogging concentration is 0.8% or more and less than 1.3%.D: The fogging concentration is 1.3% or more.

(2) Stability of Image Density

The image density was measured with a color reflection densitometer(X-RITE 404 produced by X-Rite). In the above described image outputtest, every time after standing for about one week, one sheet of solidimage was output, and the density of each image was measured. Among theresulting image densities, the difference between the maximum densityand the minimum density was determined and was evaluated on the basis ofthe criteria described below.

A: The image density difference is 0.1 or less.B: The image density difference is more than 0.1 and 0.3 or less.C: The image density difference is more than 0.3 and 0.5 or less.D: The image density difference is more than 0.5.

(3) Thin Line Reproducibility

The thin line reproducibility was evaluated from the viewpoint of imagequality. In the above described image output test, after 4,600 sheets ofimages were output, an image in which a lattice pattern with a linewidth of 3 pixels was drawn all over an A4 paper (coverage of 4% on avolume basis) was printed, and the thin line reproducibility wasevaluated on the basis of the criteria described below. The line widthof 3 pixels are 127 μm theoretically. The line width of the image wasmeasured with Microscope VK-8500 (produced by KEYENCE CORPORATION). Theline widths at 5 points selected at random were measured, the maximumvalue and the minimum value were excluded, and when an average value ofthe remaining 3 points was represented by d (μm), the thin linereproducibility index L was defined as described below.

L(μm)=|127−d|

The thin line reproducibility index L is defined as the differencebetween the theoretical line width of 127 μm and the line width d in theoutput image. The absolute value of the difference is employed in thedefinition because d may be larger than 127 or be smaller than 127.Smaller L indicates that the thin line reproducibility is excellent.

A: L is 0 μm or more and less than 5 μm (thin line reproducibility isexcellent).B: L is 5 μm or more and less than 15 μm, and slight variations in thewidth of thin line are observed (thin line reproducibility is good).C: L is 15 μm or more and less than 30 μm, and thinning and scatteringof thin line are conspicuous.D: L is 30 μm or more and breakage or thickening of thin line isobserved in places (thin line reproducibility is poor).

Examples 2 and 3, comparative Example 1

Toners 2 to 4 were produced as in Example 1 except that Silica particles1 was changed to Silica particles 2 to 4, respectively, in Example 1.Then, Toners 2 to 4 were evaluated as in Example 1. The results ofevaluation are shown in Table 2. As is clear from the results, regardingComparative example 1, the stability of image density and the thin linereproducibility (image quality) were degraded. The reason for this isestimated that the volume average particle diameter (Dv) of the silicaparticles was too small and, thereby, the silica particles were not ableto exert the effect as the spacer particles on the toner surfaces, so asto degrade the transferability.

Examples 4 and 5, Comparative Example 2

Toners 5 to 7 were produced as in Example 1 except that Silica particles1 was changed to Silica particles 5 to 7, respectively, in Example 1.Then, Toners 5 to 7 were evaluated as in Example 1. The results ofevaluation are shown in Table 2. As is clear from the results, regardingComparative example 2, all items were degraded in evaluation. The reasonfor this is estimated that the volume average particle diameter (Dv) ofthe silica particles was too large and, thereby, the silica particleswere eliminated from the toner particle surfaces easily in a long termof use, and stable chargeability and fluidity were not given to thetoner continuously.

Examples 6 to 8, Comparative Example 3

Toners 8 to 11 were produced as in Example 1 except that Silicaparticles 1 was changed to Silica particles 8 to 11, respectively, inExample 1. Then, Toners 8 to 11 were evaluated as in Example 1. Theresults of evaluation are shown in Table 2. As is clear from theresults, regarding Comparative example 3, in particular the thin linereproducibility (image quality) was degraded. The reason for this isbelieved to be that there were large variations in size of the silicaparticles, the individual particles became difficult to function asspacer particles efficiently and, thereby, the transferability wasdegraded. Furthermore, the reason is estimated that differences amongthe individual particles occurred in giving the chargeability and thefluidity to the toner, distribution of charge was extended, so as todegrade fogging and the like and, thereby stable chargeability,fluidity, and transferability were not ensured over a long term.

Examples 9 to 11, Comparative Example 4

Toners 12 to 15 were produced as in Example 1 except that Silicaparticles 1 was changed to Silica particles 12 to 15, respectively, inExample 1. Then, Toners 12 to 15 were evaluated as in Example 1. Theresults of evaluation are shown in Table 2. As is clear from theresults, regarding Comparative example 4, all items were degraded inevaluation with respect to high-temperature and high-humidity. Thereason for this is estimated that the ratio of mass decrease of Silicaparticles 15 was large and, thereby the amount of silanol groups waslarge, a large amount of water was adsorbed, the degrees of giving ofthe chargeability and the fluidity to the toner were degradedsignificantly, and stable developability and transferability were notobtained.

Examples 12 and 13

Toners 16 and 17 were produced as in Example 1 except that Silicaparticles 1 was changed to Silica particles 16 and 17, respectively, inExample 1. Then, Toners 16 and 17 were evaluated as in Example 1. Theresults of evaluation are shown in Table 2. As is clear from theresults, the thin line reproducibility (image quality) was degradedslightly. The reason for this is believed to be that the silicaparticles were obtained by a fuming method or a deflagration method, thevariation coefficient of diameters of the silica particles, based onvolume distribution thereof, is large as compared with the silicaparticles obtained by a sol-gel method and, thereby, the individualparticles became difficult to function as spacer particles efficientlyand the transferability was degraded slightly. Furthermore, the reasonis estimated that differences among the individual particles occurredslightly in giving the chargeability and the fluidity to the toner and,thereby, distribution of charge was extended, so as to degrade foggingand the like slightly.

Examples 14 and 15

Toners 18 and 19 were produced as in Example 1 except that Silicaparticles 1 was changed to Silica particles 18 and 19, respectively, inExample 1. Then, Toners 18 and 19 were evaluated as in Example 1. Theresults of evaluation are shown in Table 2. As is clear from theresults, regarding Example 15, fogging and the thin line reproducibility(image quality) were degraded slightly with respect to high-temperatureand high-humidity. The reason for this is estimated that the fixingratio of the hydrophobizing agent of Silica particles 19 was low and,thereby, in a long term of use, the hydrophobizing agent was isolatedfrom the silica particles because of the stress in the developingdevice, and stable hydrophobicity and fluidity were not obtained.

Examples 16 to 19

Toners 20 to 23 were produced as in Example 1 except that Silicaparticles 1 was changed to Silica particles 20 to 23, respectively, inExample 1. Then, Toners 20 to 23 were evaluated as in Example 1. Theresults of evaluation are shown in Table 2. As is clear from theresults, regarding Example 19, all items were degraded in evaluationwith respect to high-temperature and high-humidity. The reason for thisis estimated that the amount of surface treatment of the silicaparticles with the hydrophobizing agent was large, the degree of givingof the fluidity to the toner was reduced slightly, the start-up ofcharging of the toner was delayed slightly and, thereby, when the imagewas output after a long term of standing, fogging and thetransferability were degraded slightly.

Example 20

Toner 24 was produced as in Example 1 except that Silica particles 1 waschanged to Silica particles 24 in Example 1. Then, Toner 24 wasevaluated as in Example 1. The results of evaluation are shown in Table2. As is clear from the results, good results were obtained.

TABLE 2 Low-temperature low-humidity environment High-temperaturehigh-humidity environment Fogging Stability of image Thin line FoggingStability of image Thin line (measured density (measured reproducibility(measured density (measured reproducibility Toner Silica particlesvalue) value) (measured value) value) value) (measured value) Example 1Toner 1 Silica particles 1 A(0.1) A(0.1) A(3) A(0.1) A(0.1) A(3) Example2 Toner 2 Silica particles 2 A(0.2) A(0.1) A(4) A(0.2) A(0.1) A(4)Example 3 Toner 3 Silica particles 3 B(0.5) B(0.2) C(18) B(0.4) B(0.2)C(17) Comparative Toner 4 Silica particles 4 C(1.0) D(0.7) D(31) C(0.7)D(0.5) D(30) example 1 Example 4 Toner 5 Silica particles 5 A(0.2)A(0.1) A(4) A(0.2) A(0.1) A(4) Example 5 Toner 6 Silica particles 6B(0.8) C(0.4) C(19) B(0.5) C(0.4) C(22) Comparative Toner 7 Silicaparticles 7 D(1.8) D(0.6) D(30) D(1.5) D(0.5) D(32) example 2 Example 6Toner 8 Silica particles 8 A(0.2) A(0.1) A(4) A(0.2) A(0.1) A(4) Example7 Toner 9 Silica particles 9 B(0.4) B(0.2) B(8) B(0.5) B(0.2) B(9)Example 8 Toner 10 Silica particles 10 B(0.6) B(0.3) C(16) C(1.0) B(0.3)C(18) Comparative Toner 11 Silica particles 11 C(1.3) C(0.5) D(30)D(1.8) C(0.4) D(31) example 3 Example 9 Toner 12 Silica particles 12A(0.2) A(0.1) A(4) A(0.2) A(0.1) A(4) Example 10 Toner 13 Silicaparticles 13 B(0.3) B0.3) B(5) B(0.4) B(0.2) B(7) Example 11 Toner 14Silica particles 14 B(0.8) C(0.4) B(12) C(0.9) C(0.4) B(14) ComparativeToner 15 Silica particles 15 C(1.2) D(0.7) C(29) D(1.6) D(0.6) D(33)example 4 Example 12 Toner 16 Silica particles 16 B(0.8) B(0.3) C(23)C(0.9) B(0.3) C(27) Example 13 Toner 17 Silica particles 17 B(0.8)B(0.3) C(22) C(0.9) B(0.3) C(24) Example 14 Toner 18 Silica particles 18B(0.4) B(0.2) B(7) B(0.7) B(0.2) B(6) Example 15 Toner 19 Silicaparticles 19 B(0.8) B(0.3) C(16) C(1.0) B(0.3) C(23) Example 16 Toner 20Silica particles 20 A(0.2) A(0.1) A(4) A(0.2) A(0.1) A(4) Example 17Toner 21 Silica particles 21 B(0.3) B(0.2) B(6) B(0.3) B(0.2) B(8)Example 18 Toner 22 Silica particles 22 B(0.5) C(0.4) B(8) C(0.8) B(0.3)B(12) Example 19 Toner 23 Silica particles 23 B(0.7) C(0.4) B(12) C(1.1)C(0.4) C(17) Example 20 Toner 24 Silica particles 24 A(0.2) A(0.1) B(5)A(0.2) A(0.1) B(5)

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2010-251905 filed Nov. 10, 2010, which is hereby incorporated byreference herein in its entirety.

1. A toner comprising: toner particles, each of which contains a binderresin and a colorant, and silica particles; wherein the silica particleshave a volume average particle diameter (Dv) of 70 nm or more and 500 nmor less, the variation coefficient of diameters of the silica particles,based on volume distribution thereof, is 23% or less, and wherein whenheating the silica particles to measure the mass variation, the ratio ofmass decrease of the silica particles at the temperature in the range of105° C. to 200° C. is 0.60% or less.
 2. The toner according to claim 1,wherein the silica particles are produced by a sol-gel method.
 3. Thetoner according to claim 1, wherein the silica particles are treatedwith a hydrophobizing agent, and the fixing ratio of the hydrophobizingagent to the silica particles is 90% or more.
 4. The toner according toclaim 3, wherein the silica particles have the amount of carbon derivedfrom the hydrophobizing agent of 0.01% by mass or more and 4.5% by massor less.